Communication devices, such as wireless devices, are enabled to communicate wirelessly in a radio communications system, sometimes also referred to as a radio communications network, a mobile communication system, a wireless communications network, a wireless communication system, a cellular radio system, or a cellular system. The communication may be performed via a radio channel, e.g., between two wireless devices, between a wireless device and a regular telephone, and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the wireless communications network.
A cellular radio system covers a geographical area which is divided into cell areas, wherein each cell area is served by a network node such as a Base Station (BS), e.g., a Radio Base Station (RBS), which sometimes may be referred to as, e.g., eNB, eNodeB, NodeB, or BTS (Base Transceiver Station), depending on the technology and terminology used. A cell is the geographical area where radio coverage is provided by the base station at a base station site.
Wireless devices are also known as, e.g., user equipments, mobile terminals, wireless terminals and/or mobile stations, mobile telephones, cellular telephones, or laptops with wireless capability, just to mention some examples. The wireless devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data with another entity.
Code Division Multiple Access (CDMA) is a radio channel access method used by various radio communication technologies, such as, for example, Wideband Code Division Multiple Access (WCDMA). WCDMA is a mobile phone standard used in various mobile phone systems, such as for example the Universal Mobile Telecommunications System (UMTS).
Wireless devices require a lot of processing power. For example, these devices make use of energy consuming receivers such as, e.g., a computational-intensive rake receiver. A rake receiver is a receiver designed to counter the effects of multipath propagation, such as multipath fading. It does this by using several “sub-receivers” called fingers. The fingers are correlators, each of which is assigned to a different multipath component. Each finger independently decodes a single multipath component. At a later stage, the contribution of all fingers is combined in order to make the most use of the different transmission characteristics of each transmission path.
The multipath channel through which a radio wave transmits can be viewed as transmitting the original, i.e., line of sight, wave pulse through a number of multipath components. Multipath components are delayed copies of the original transmitted wave traveling through a different echo path, each with a different magnitude and time-of-arrival at the receiver. Since each component contains the original information, if the magnitude and time-of-arrival (phase) of each component is computed at the receiver, through a process called channel estimation, then all the components can be added coherently to improve the information reliability.
Moreover, wireless devices may use sophisticated Forward Error Correction (FEC) decoders, like turbo decoders, which also consume a lot of energy. A turbo decoder decodes the output signal from the rake receiver. The turbo decoder is constructed from two decoders: an interleaver and a deinterleaver. The turbo decoding algorithm may run multiple times on the same data to improve the output of the turbo decoder. A turbo decoder has a better performance than a conventional decoder due to this iterative algorithm. However, the power consumption also increases as the number of iterations increases.
To achieve an acceptable usage time before the battery is empty, an energy-efficient architecture is a vital requirement. Low power hardware is a first requirement to achieve an energy efficient architecture. Additionally, optimal control of this low power hardware is needed to save energy consumption. Furthermore, an adequate quality of a wireless link between the wireless device and a second radio node, such as a base station, is desired. This is not trivial due to the changing conditions of the external environment.